1. Field of the Invention
The present invention relates to a fabric feeding device and a fabric feed control device of a sewing machine.
2. Discussion of the Prior Art
A commonly known feed adjusting device of a sewing machine is adapted such that the feed distance or amount or stitch length is adjustable by an operator-controlled member within a range in which stitching is possible in the sewing machine. An example of this conventional type of feed adjusting mechanism is shown in FIG. 23, which includes a feed dog 1 for feeding a work fabric, a drive lever 2 for reciprocating the feed dog, a drive cam 3 rotated by a drive shaft (not shown) or a rotary shaft (not shown) driven by the drive shaft, an oscillating rod 4 oscillated by the drive cam 3, a feed regulator 5 associated with the oscillating rod 4 so as to adjust the distance of reciprocation of the feed dog 1 through the drive lever 2, and a feed adjusting cam 6 which is formed integrally with or operatively connected to an operator-controlled member 7, to control the feed regulator 5.
Sewing machines of modern vintage are generally capable of forming a variety of stitching patterns such as buttonhole patterns and so-called "super patterns" on a work fabric. The super patterns are stitching patterns such as super zigzag decorative stitches and triple stitches, which are formed by a combination of forward and reverse stitching actions with the fabric being fed in respective forward and reverse directions. Such sewing machines are adapted to form such patterns by a combination of forward and reverse stitching operations. For example, the sewing machine is arranged such that right and left side parts of a buttonhole pattern are sewn during forward and reverse fabric feeding operations, respectively. Where such a sewing operation is performed on a stretch fabric having a relatively high degree of elasticity, there may arise a considerable difference between the actual fabric feed distances in the forward and reverse fabric feeding operations even when the feed distance of the feed dog is the same in the forward and reverse feeding operations. This difference in the actual fabric feed distance results in a deviation of the sewn pattern from the nominal pattern. In view of this drawback, the recent sewing machines are required to have a fine feed adjustment device capable for intricately adjusting the feed distances of the feed dog in the forward and reverse feeding operations independently of each other, for establishing an optimum balance between the actual forward and reverse fabric feed distances. This fine adjustment device is reqired to:
1) make fine adjustment of the forward and reverse feed distances relative to each other (within a range between about 0.2 mm and about 1 mm, for example) in the feeding operations to form the right and left side parts of a buttonhole pattern, for establishing the optimum balance of the actual forward and reverse fabric feed distances, such that the fine adjustment for the side parts of the buttonhole pattern does not affect the fabric feed distance in the other sewing operations; and PA1 2) make fine adjustment of the forward and reverse feed distances relative to each other in feeding operations to form super patterns (for establishing the optimum balance of the actual forward and reverse fabric feed distances), such that the fine adjustment for the super patterns does not affect the fabric feed distance in the other sewing operations.
Such a fine feed adjustment device for the right and left side parts of buttonhole patterns is disclosed in JP-Y2-58-18856 (laid-open publication for opposition purpose of Japanese Utility Model Application No. 53-155714). This fine feed adjustment device is capable of adjusting the forward and reverse feed distances for the right and left side parts of a buttonhole pattern and making fine adjustment thereof, but is not capable of adjusting the forward and reverse feed distances in the sewing of super patterns. Namely, the fine feed adjustment device is arranged such that shaft 19 and feed regulator 1 engage each other through adjusting pin 9 and other members 6, 7. The engagement of the shaft 19 with the adjusting pin 9 prevents oscillating movements of the feed regulator 1, which are necessary for stitching the super patterns. The fine adjustment of the feed distances for the right and left side parts of the buttonhole pattern undesirably affects the feed distances in the other sewing operations except for the stitching of the super patterns.
JP-Y2-59-8687 (laid-open publication for opposition purpose of Japanese Utility Model Application No. 55-30688) discloses a fine feed adjustment device wherein fine feed adjustment for the right and left side parts of the buttonhole pattern affects the feed distances in the other sewing operations including the stitching of the super patterns. According to this device, the fine adjustment of the forward and reverse feeding distances for the side parts of the buttonhole pattern may disturb the balance between the forward and reverse feed distances in a subsequent sewing operation to form a super pattern, and the fine feed adjustments must be made again for the sewing operation to form the super pattern. This fine feed adjustment device suffers from a similar problem when a buttonhole sewing operation is effected following a sewing operation to form a super pattern.
JP-B2-58-31946 (laid-open publication for opposition purpose of Japanese Patent Application No. 50-41982) discloses a fine feed adjustment device which is adapted so as to maintain feed adjustments which have been made last for the right and left side parts of a buttonhole pattern, even after any other sewing operation, so that the feed adjustments made last for the buttonhole pattern are available for that buttonhole pattern which is to be sewn after the above-indicated other sewing operation. Accordingly, this device eliminates a need of re-adjustment of the forward and reverse feed distances for that buttonhole pattern, which would require a trial or test sewing operation. Further, the feed adjustments for the buttonhole patterns do not affect the feed distances in the other sewing operations. In addition, this fine feed adjustment device is considered to be capable of effecting fine feed adjustments for super patterns.
Although the fine feed adjustment device disclosed in the publication JP-B2-58-31946 is considered to be the best of all discussed above in terms of operating efficiency and feed adjusting functions, the use or application of this type of device is limited to certain types of sewing machines, due to the use of three feed cams which are superposed on each other, for the right and left side parts of a buttonhole pattern and a bar tack part of the buttonhole pattern, respectively, as shown in FIG. 3 of the publication. In this respect, it is noted that the feed distance is zeroed during stitching to form the bar tack. A cam follower device following these three cams is needed, and this cam follower device is required to be movable in the direction in which the cams are superposed on each other. However, such a cam follower device is not necessarily provided on sewing machines currently available. Therefore, the fine feed adjustment device is not applicable to a sewing machine not provided with the cam follower device, or to a sewing machine in which the cam follower device is not movable.
JP-B2-56-50997 (laid-open publication for opposition purpose of Japanese Patent Application No. 50-98833) discloses a fine feed adjustment device capable of effecting fine feed adjustments for optimizing a balance between the forward and reverse fabric feed distances in sewing operations to form super patterns. However, this device is not completely satisfactory to make fine adjustment for the forward and reverse feed distances for the right and left side parts of a buttonhole, since the same operator-controlled member is used and operated in the same manner (rotated) for making the fine feed adjustments for all patterns including buttonhole patterns. More specifically described, the device is not able to make fine adjustment to establish an optimum balance between the actual right and left fabric feed distances once the feed adjustments have been made for the right and left side parts. While the device is highly accurate in the feed cam device, it is not suitable for the fine feed adjustments.
Thus, the known feed adjusting devices except for the device of JP-B2-58-31946 are not capable of making fine adjustment for the forward and reverse feeding distances for both the super patterns and the right and left side parts of buttonholes. Although the feed adjusting device of JP-B2-58-31946 is capable of the fine adjustment for both the super patterns and the buttonhole patterns, this device requires a movable cam follower device, which limits the type of the sewing machine to which the feed adjusting device is applicable.